The invention relates to a "digital linear actuator", composed of a plurality of sequentially connected digital actuator cells each of which contracts in response to a corresponding digital signal.
Various mechanisms are known for producing controlled movement of a mechanical element or a connecting point thereof. For example, hydraulic and pneumatic cylinders are commonly used to produce forceful movement of arms and other mechanical elements of numerous mechanical, prosthetic, and/or robotic devices. Jackscrews which are rotated in a controlled fashion by stepper motors or servo motors in response to digital or analog control systems are widely used. Various cable and pulley assemblies and various chain and sprocket mechanisms also are commonly used to produce controlled movement of mechanical devices. Electrical solenoids and other electromagnetic devices also are commonly used to provide forceful movement of mechanical elements in response to suitable control signals. However, none of the above mechanical actuators and devices for producing forceful movement in a controlled fashion are really completely satisfactory for many of the applications in which they are commonly used. For example, in prosthetic devices in which the contraction of a human or animal muscle must be simulated, none of the above mechanical movement producing devices is entirely satisfactory because most of the devices mentioned above are too large in size and too great in mass to be ideal for controlling precise movement in prosthetic or robotic devices. All of the above mechanical movement-producing devices fail to provide a combination of features including smallness in size and mass, precision of controlling movement in response to digital signals, and very high force-producing capability that would be desirable in many prosthetic and robotic applications. Furthermore, most of the above mechanical movement-producing devices experience various other shortcomings in certain environments, for example, in environments in which there are corrosive ambient conditions or higher concentrations of abrasive and/or defect-causing dust or other minute particulates.
There is clearly a presently unfulfilled need for a type of device, referred to herein as a "digital linear actuator", which can produce precisely controlled, approximately linear movement of mechanical elements or connecting points in response to digital control information, and especially such a device that can fairly precisely simulate the contracting behavior of a muscle in response to the digtal control information, especially in a prosthetic or robotic device.